Axiom Chirp and Downvision images

[stans2000]

I tested my Axiom this weekend and couldn't figure out why I was seeing fish using the Chirp screen, but not on the Downvision. I could see the bottom of the bay, but no fish. Is there a setting on the Downvision that I'm not aware of?

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Stan,

Please click here to view a FAQ addressing coverage footprints and difference between of CHIRP (conical) and DownVision sonar.

[stans2000]

So, what does all this mean when I am in 10 feet, 20 feet, 40 feet and 60 feet of water and I don't see any fish on the downvision, but I do on the Chirp

[Chuck - Raymarine - Moderator]

Stan,

Per the previously referenced FAQ, the base of cone being scanned by each ping when using CHIRP conical sonar is equal to 0.4434 * Depth. At 10', 20', 40', and 60' depths, the diameter of the base is 4.4', 8.9', 17.7', 26.6'. The angle of the beam produced by DownVision is significantly larger side to side axis than in the fore-aft axis. In contrast, the fore/aft dimensions being scanned by each ping when using DownVision is equal to 0.01222 * Depth. At 10', 20', 40', and 60' depths, the diameter of the fore/aft area being scanned with each ping is 0.1', 0.2', 0.4888, and 0.7332. The side to side area being scanned with each DownVision ping may be similarly obtained based on depth using the multiplier found within the referenced FAQ. As specified within the referenced FAQ, it is the differences in the shape of the area being swept by CHIRP and DownVision combined with color variation based upon strength of the sonar returns which make CHIRP (conical) sonar the sonar of choice for marking fish and DownVision the choice of choice of these two types of sonar when seeking the greatest detail for bottom structure and objects within the water column. Marking fish with DownVision may be enhanced through manual increases to the DownVision sonar Sensitivity settings (MENU->SENSITIVITY SETTINGS). While it is often possible for DownVision to show fish, it is generally recommended that CHIRP be used for this purpose.

[Marinerjoe]

One thing I discovered over the weekend is how to use the zoom. FYI, I have a Axiom 7 RV with dual 20 degree thru-hull transducers.

Prior to my last outing on Monday, I hadn't messed with any adjustments other than the color palates for the sounder screens. Shortly after we got underway, I had the screen in a 2-way split with side-vision on one side, and 3D on the other. I wasn't seeing much that excited me, and was wondering why my e165/CP370 (not connected yet to the Axiom) was seeing much more.

I went and increased the zoom on the Axiom, which I hadn't done before, on the side-vision window. The narrow view expanded, and simultaneously the 3-D view also expanded. I was very happily surprised at that. The rest of the trip my friend and I spent it drifting and powering back and forth over a wreck in ~ 60' of water, experimenting with the zoom and other controls.

Not sure if this will help you, but messing with the zoom DEFINITELY helped me and got me MUCH MORE excited about the Axiom sounder capabilities.

Good luck,

Joe

[stans2000]

I' going out again this weekend and I will let you know the results. Thanks

[Chuck - Raymarine - Moderator]

You're welcome.